This patch adds a new class for dm-delay that delays flush requests. Previously, flushes were delayed as writes, but it caused problems if the user needed to create a device with one or few slow sectors for the purpose of testing - all flushes would be forwarded to this device and delayed, and that skews the test results. This patch allows to select 0 delay for flushes.
Signed-off-by: Mikulas Patocka <[email protected]> --- Documentation/device-mapper/delay.txt | 2 +- drivers/md/dm-delay.c | 34 ++++++++++++++++++++++++++++++---- 2 files changed, 31 insertions(+), 5 deletions(-) Index: linux-2.6/drivers/md/dm-delay.c =================================================================== --- linux-2.6.orig/drivers/md/dm-delay.c 2018-04-17 00:13:44.000000000 +0200 +++ linux-2.6/drivers/md/dm-delay.c 2018-04-17 00:21:11.000000000 +0200 @@ -34,6 +34,7 @@ struct delay_c { struct delay_class read; struct delay_class write; + struct delay_class flush; int argc; }; @@ -126,6 +127,8 @@ static void delay_dtr(struct dm_target * dm_put_device(ti, dc->read.dev); if (dc->write.dev) dm_put_device(ti, dc->write.dev); + if (dc->flush.dev) + dm_put_device(ti, dc->flush.dev); mutex_destroy(&dc->timer_lock); @@ -171,8 +174,8 @@ static int delay_ctr(struct dm_target *t struct delay_c *dc; int ret; - if (argc != 3 && argc != 6) { - ti->error = "Requires exactly 3 or 6 arguments"; + if (argc != 3 && argc != 6 && argc != 9) { + ti->error = "Requires exactly 3, 6 or 9 arguments"; return -EINVAL; } @@ -198,12 +201,25 @@ static int delay_ctr(struct dm_target *t ret = delay_class_ctr(ti, &dc->write, argv); if (ret) goto bad; + ret = delay_class_ctr(ti, &dc->flush, argv); + if (ret) + goto bad; goto out; } ret = delay_class_ctr(ti, &dc->write, argv + 3); if (ret) goto bad; + if (argc == 6) { + ret = delay_class_ctr(ti, &dc->flush, argv + 3); + if (ret) + goto bad; + goto out; + } + + ret = delay_class_ctr(ti, &dc->flush, argv + 6); + if (ret) + goto bad; out: dc->kdelayd_wq = alloc_workqueue("kdelayd", WQ_MEM_RECLAIM, 0); @@ -269,7 +285,10 @@ static int delay_map(struct dm_target *t struct dm_delay_info *delayed = dm_per_bio_data(bio, sizeof(struct dm_delay_info)); if (bio_data_dir(bio) == WRITE) { - c = &dc->write; + if (unlikely(bio->bi_opf & REQ_PREFLUSH)) + c = &dc->flush; + else + c = &dc->write; } else { c = &dc->read; } @@ -289,7 +308,7 @@ static void delay_status(struct dm_targe switch (type) { case STATUSTYPE_INFO: - DMEMIT("%u %u", dc->read.ops, dc->write.ops); + DMEMIT("%u %u %u", dc->read.ops, dc->write.ops, dc->flush.ops); break; case STATUSTYPE_TABLE: @@ -299,6 +318,10 @@ static void delay_status(struct dm_targe DMEMIT(" "); EMIT_CLASS(&dc->write); } + if (dc->argc >= 9) { + DMEMIT(" "); + EMIT_CLASS(&dc->flush); + } #undef EMIT_CLASS break; } @@ -316,6 +339,9 @@ static int delay_iterate_devices(struct ret = fn(ti, dc->write.dev, dc->write.start, ti->len, data); if (ret) goto out; + ret = fn(ti, dc->flush.dev, dc->flush.start, ti->len, data); + if (ret) + goto out; out: return ret; Index: linux-2.6/Documentation/device-mapper/delay.txt =================================================================== --- linux-2.6.orig/Documentation/device-mapper/delay.txt 2017-06-03 00:22:35.000000000 +0200 +++ linux-2.6/Documentation/device-mapper/delay.txt 2018-04-17 00:24:22.000000000 +0200 @@ -5,7 +5,7 @@ Device-Mapper's "delay" target delays re and maps them to different devices. Parameters: - <device> <offset> <delay> [<write_device> <write_offset> <write_delay>] + <device> <offset> <delay> [<write_device> <write_offset> <write_delay> [<flush_device> <flush_offset> <flush_delay>]] With separate write parameters, the first set is only used for reads. Offsets are specified in sectors. -- dm-devel mailing list [email protected] https://www.redhat.com/mailman/listinfo/dm-devel
